The present invention is a process for the preparation of hydrolyzable beta-cyanoalkylsilanes. More particularly, this invention relates to the catalytic addition of silicon hydrides to alpha,beta-unsaturated olefinic nitriles to form betacyanoalkylsilanes. The present invention employs a novel catalyst comprising an aminoorganosilane.
Hydrolyzable beta-cyanoalkylsilanes are useful for the production of polyorganosiloxanes containing the beta-cyanoalkyl substituent. The silicon-bonded beta-cyanoalkyl radical is extremely resistant to hydrolysis and cleavage under hot, humid conditions. Therefore, the beta-cyanoalkylsilanes find particular use in the preparation of polyorganosiloxanes which must be subjected to hot, humid conditions. The presence of the silicon-bonded beta-cyanoalkyl radical substituted on polyorganosiloxanes also tends to stabilize the polyorganosiloxanes against swelling induced by liquid hydrocarbons.
Jex et al., U.S. Pat. No. 2,906,764, issued Sept. 29, 1959, describe a process for producing cyanoalkylsilanes by reacting an olefinic nitrile with a silane, the silane having at least one hydrogen and one hydrolyzable group bonded to the silicon atom, in the presence of a diarylamine catalyst.
Pike et al., J. Org. Chem. 24, 1939-42, 1959, describe tertiary amines as effective directive catalysts for the reaction of trichlorosilane with acrylonitrile to form beta-cyanoethyltrichlorosilane.
Pike et al., J. Org. Chem. 27, 2190-92, 1962, describe preparation of beta-cyanoethyltrichlorosilane by reacting trichlorosilane with acrylonitrile in the presence of silylamine catalysts of the general formula (CH.sub.3).sub.3 SiNR.sub.2, where the nitrogen atom of the silylamine is attached to the silicon atom. Pike et al. postulate that some of the amino groups from these silylamines probably rearrange with the chloro groups of the trichlorosilane to form a silylamine of formula HSi(NR.sub.2)Cl.sub.2, which silylamine may be the actual catalyst for the reaction of trichlorosilane with acrylonitrile.
The present process employs a novel catalyst comprising an aminoorganosilane. The nitrogen atoms of the aminoorganosilane are present in amino radicals that are attached to a carbon radical which is in turn attached to silicon through a silicon-carbon linkage. The nitrogen atoms are not attached directly to the silicon atoms. The described aminoorganosilanes promote the beta-hydrosilylation of unsaturated olefinic nitriles by silicon hydrides.